Bonded aggregate composition and binders for the same

ABSTRACT

Bonded aggregate compositions such as concrete, concrete repair products, high temperature refractories, high temperature insulation and fire resistant insulation are made from an aqueous solution of phosphoric acid and a separate, storable dry mixture of suitable aggregate, monocalcium phosphate, and calcium in the form of calcium aluminate cement or calcium oxide. The proportion of wet to dry constituents is variable so as to select the working time and strength of the aggregate composition, typically on the order of ten to fifteen minutes. The mixture of the preferred dry constituents, and the binder to be mixed with the aggregate to yield the preferred dry mixture, are also disclosed. The binder system is particularly advantageous in that the same set of binder constituents can readily be employed with a variety of aggregates, reducing the cost of providing a variety of aggregate compositions due to the ready availability of the raw materials and obviating the need to stock different binders for different aggregate compositions. Cost is additionally reduced through the use of less purified, and therefore less expensive constituents.

The present application is a continuation of 09/280,608 filed Mar. 29,1999, abandoned which is a continuation-in-part of 08/846,816 filed Apr.30, 1997, U.S Pat. No. 5,888,292, which is a continuation of 08/703,837filed Aug. 27, 1996, abandoned which is a continuation of 08/477,774filed Jun. 7, 1995, abandoned which is a continuation-in-part of08/253,613 filed Jun. 3, 1994, abandoned which is a continuation of07/874,377 filed Apr. 27, 1992 abandoned.

FIELD OF THE INVENTION

The present invention relates to bonded aggregate structures usedprimarily for high temperature applications. More particularly, thepresent invention relates to materials required to protect holdingvessels containing both ferrous and non-ferrous metals, molten glass,and airborne high temperature environments such as boilers and furnacesof all kinds. The present invention further relates to the compositionfor forming such structures and binders for use in such compositions.

BACKGROUND OF THE INVENTION

Bonded aggregate compositions are a class of known materials useful formany purposes. The class includes such products as concrete repairmaterials, heat resistant floor materials, high temperature refractorymaterials, high temperature insulation materials, and fire resistantmaterials. Bonded aggregate compositions generally comprise a suitableaggregate (a filler which determines the structural characteristics ofthe compositions before and after heat up) bound by a binder such as ahigh temperature cement.

Conventional cements used for bonding aggregates include aluminouscements, hydraulic cements, and Portland cements. Hydraulic cements aremixtures of fine ground lime, alumina, and silica which set to a hardproduct upon admixture with water, the water combining chemically withthe cement constituents to form a hydrate. Portland cements areparticularly hydraulic cements composed of lime, alumina, silica, andiron oxide (as tetracalcium aluminoferrate), tricalcium aluminate,tricalcium silicate, and dicalcium silicate. Portland cements containgenerally less than five percent alumina.

Aluminous cements, in contrast, are hydraulic cements which contain atleast thirty to thirty-five percent alumina, which is usually applied bythe inclusion of calcined bauxite.

The cement or binder is selected to match the particular use for whichthe bonded composition will be used and to match the particularaggregate employed, which is similarly chosen in view of the ultimateuse of the bonded composition.

Binder systems based upon phosphates have been employed, but the use ofsuch systems normally include phosphoric acid (or a salt thereof in thepresence of water) in combination with an inorganic metal oxide such asmagnesium oxide or alumina oxide. Two types of products can be formedfrom such systems: some experiencing high temperatures during settingwhile ultimately achieving a high p.s.i. strength and achieving a quickset of the product at ambient temperature (15 degrees F to 85 degreesF), and others having a controlled set by application of significantheat (200 degrees F to 500 degrees F) to bring about a final set. Themajor drawbacks of these systems are the short working times availablefor the ambient set formulations, which are typically on the order ofone minute. While it is preferred in working with bonded aggregates ofany type that the composition set fairly rapidly, a working time of atleast three minutes and preferably a range of seven to ten minutes ismost desirable. With controlled set the user is extremely limited as towhere the materials can be used. Both of these compositions are verysensitive to impurity when exposed to temperatures above 2500 degrees F.This limits their use both from an economic as well as practical pointof view.

SUMMARY OF THE INVENTION

Applicant has discovered that the problems of the control of the settingspeed of the aggregate composition, the sensitivity of the compositionto impurities and the additional costs associated with providing avariety of binders for different aggregates can all be overcome by theuse of a binder system comprising at least one phosphate-providingcomponent which is in a liquid phase at ambient temperature andpressure, and at least one dry component containing CaO, Al₂O₃, SiO₂,and Fe₂O₃. In one embodiment, the dry component comprises acalcium-providing component, a magnesium-providing component, ormixtures thereof. The binder may, but does not have to contain, a dryphosphate-providing component. In one embodiment, a dryphosphate-providing component and a calcium-providing component arepreferably contained in a single material such as hydrated monocalciumphosphate (Ca H₂PO₄ H₂O). However, although these two components arecontained in a single material in this embodiment, an additionalcalcium-providing material (such as calcium aluminate cement, calciumoxide, or mixtures of them) is preferred.

Strength and dimensional characteristics can be controlled byselectively varying the concentration and ratio of the wet and drycomponents. The invention permits the use of commercial or preferablyagricultural grade materials having lower cost than the highly purifiedconstituents presently required in other systems. This invention doesnot have as a requirement the use of technical grade components, inparticular technical grade phosphoric acid, as is required in othersystems.

The invention is also directed to an admixture of only the dry bindercomponents, wherein the binder is mixed with the aggregate and the wetphosphate-providing component at a remote location or where the boundaggregate structure is to be formed.

A basis for bonding in one preferred system is believed to be theadmixture of a calcium-providing component such as a calcium aluminatewith a wet phosphate-providing constituent such as a dilute phosphoricacid. Applicant has found that the optional addition of a dryphosphate-providing component to the basic binder not only varies thesetting time by a controllable amount, but varying the percentagestrengths of the aqueous phosphates to the percentage strengths of thedry phosphates, also alters the strengths and refractory characteristicsof the aggregate structures after they are heated.

The binder of the present invention can typically be employed with avariety of aggregate structures, such as refractory structures, hightemperature insulation structures, ambient temperature structures suchas regular floor and road applications, fire resistant structures, aswell as a repair material for these high-and ambient-temperaturestructures. One particularly useful ambient temperature applicationinvolves the use of this system for the overall containment andneutralization of harmful liquid wastes, such as radioactive wastes. Forexample, the binder of the present invention can be used in conjunctionwith a phosphate-containing aggregate to both neutralize the waste, aswell as contain it, either by hardening the waste itself or “walling” itin. In this way, environmental seepage of the harmful waste is avoided.

The optional dry phosphate-providing component of the present inventionpreferably also contains a calcium-providing component in a singlematerial such as monocalcium phosphate, while the wetphosphate-providing component is typically a phosphoric acid solution,preferably an agricultural grade solution. In one embodiment, anadditional calcium-providing component is included in the binder, thusthe additional calcium-providing component usually comprises either acalcium aluminate cement or calcium oxide or a mixture of thesematerials.

The dry aggregate composition in accordance with the present inventiontypically comprises between fifty and ninety-five percent by weight ofthe aggregate, one to twenty-five percent by weight of a dry componentcontaining CaO, Al₂O₃, SiO₂, and Fe₂O₃ and zero to fifty percent byweight of the dry phosphate-providing component. Such a dry aggregatecomposition can be admixed with about five to eighty-five percent byweight of a wet phosphate-providing component, such as a solution ofcommercially available phosphoric acid solution.

The present invention is thus not only directed to the bonded aggregatecomposition or structure, but is also directed to a dry bindercomprising a mixture of the optional dry phosphate component, the wetphosphate component and the calcium component, and also to a dryaggregate composition useful for forming an aggregate structure upon theaddition of a wet phosphate component. In this situation, the dryaggregate composition comprises an aggregate, an optional dry phosphatecomponent and a dry calcium and/or magnesium component. The invention isalso directed to a method of forming a bonded aggregate structurecomprising the steps of mixing a wet phosphorous-providing componentwith the dry aggregate composition, forming the admixture into anappropriate shape, and allowing the admixture to set.

As noted, the specific proportions of components optimal for aparticular purpose can readily be selected on a trial-and-error basis,but in any event are selected so as to be adequate to achieve a bondedaggregate composition of adequate strength and utility after admixtureand working. It is believed, however, that the wet-to-dry ratios aregoverned by the structural requirements of the finished, cured aggregatestructure. Generally a lower wet-to-dry ratio will be expected to resultin a bonded aggregate structure of higher strengths and stability.Dilution of the aqueous phosphate while increasing the proportion of,for example, dry phosphate and calcium aluminate, is expected to yieldmaterials having high strengths in a lower temperature range (1200 F to2200 F), but suffering structural failure above that range. Increasingthe phosphate content in the aqueous component while simultaneouslydecreasing the proportions of, for example, dry phosphate and calciumaluminate, is expected to yield materials having high strengths in ahigher temperature range (2200 F-3100 F) and to simultaneously extendthe limit of structural failure to a higher temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A better understanding of the present invention will now be had uponreference to the following detailed examples falling within the scope ofthe appended claims. A bonded aggregate structure according to thepresent invention is generally formed by the admixture of aphosphate-providing component which is in a liquid phase at ambienttemperature and pressure, with a previously constituted admixture of drycomponents including an aggregate, and a component containing an elementselected from the group consisting of Group IIA elements, preferably acalcium- or magnesium-providing component or a mixture thereof. In oneembodiment, calcium aluminate cement is utilized. Finally, an optionaldry phosphate providing component may be added to the dry components.The proportions of these components in various compositions are setforth in the following examples.

The wet phosphate-providing component is preferably a dilute solution ofagricultural grade phosphoric acid or orthophosphoric acid, althoughcommercial, industrial and technical grades can also be used. The wetphosphate-providing component is added in an amount adequate to renderthe admixture workable yet also adequate to provide a sufficientphosphate content to permit rapid setting, on the order of 8 to 30minutes at 70 degrees F such that the admixture can be applied to a moldor shaped to form a bound aggregate structure. Molds can be constructedof materials such as steel, wood, foam, plastic and combinations thereofThe bound aggregate structure can be removed from mold after if after ithas set. An aggregate can be readily formed from batches of theaggregate and dry component mixture, mixed with an appropriate amount ofphosphoric acid solution.

A wet phosphate-providing component especially useful for refractory orhigh temperature insulation aggregates is shown in the examples and wasprepared as a 1:1 to 4:1 dilution (water:acid) of TG-434, anorthophosphoric acid of H₃PO₄ available from PCS Sales, Inc., Aurora,N.C. A typical composition for TG-434 is:

H₃PO₄ 77.73% Solids  0.1% Iron as Fe₂O₃  1.3% Aluminum as Al₂O₃  0.6%Magnesium as MgO  1.3% Fluoride as F  0.5% Sulphate as SO₄  0.8% Calciumas CaO  0.2% Arsenic as As  0.5 ppm Organic Carbon as TOC 55.0 ppm H₂OBalance

TG-434 is a light green liquid having a specific gravity of 1.71 and anapparent Brookfield viscosity of 150 centipoise at 75 degrees F. Itsfreezing point at a concentration of 56.3% P₂O₅ is below −20 degrees F.

The aqueous or wet phosphate-providing component can alternatively beany liquid phosphate which is capable of providing dimensional andstructural stability to the bonded aggregate structure when exposed toelevated temperature up to 3,400 degrees F. This component can also bepackaged to include aggregate disposed therein.

The optional dry phosphate-providing component can be any materialcontaining a water soluble phosphate in a concentration adequate toreact with the calcium- or magnesium-providing component to provide anadequate bond to the aggregate structure.

The preferred dry phosphate-providing component is monocalcium phosphateor triple superphosphate of formula Ca(H₂PO₄)₂ H₂O sold as C-38 from PCSSales, Inc., Aurora, N.C. A typical composition for C-38 is:

P₂O₅ 67.1% Calcium, as CaO 20.9% Fluoride compounds as F  1.7% Al₂O₃0.40% SiO₂  1.7% Fe₂O₃  1.8% MgO  2.0% SO₄  3.0%

The advantage in using a monocalcium phosphate is that you are combiningboth a phosphate providing component and a calcium providing componentin one material. C-38 is an odorless, gray, granular solid having aspecific gravity between 1.1 and 1.2 and possessing a melting point of230 degrees F. A 1 % suspension in water has a pH of between about 2.5to 2.8.

The additional calcium- or magnesium-providing component can be anymaterial capable of providing supplemental calcium or magnesium to reactwith the phosphate components in order to provide adequate bonding inthe aggregate structure. A dry calcium binder component can include thecompounds of CaO, Al₂O₃, SiO₂, and Fe₂O₃. Calcium aluminate cements suchas Secar, Lumnite, Refcon CaO Al₂O₃, CaO Al₂O₃ Fe₂O₃, CaO Al₂O₃ SiO₂, orCaO Al₂O₃ SO₄ are preferred materials, as well as long-working calciumaluminate cements (to extend both the working time and the setting time)and magnesium oxides.

A particularly preferred additional calcium-providing material is thecalcium aluminate cement sold under the name Refcon™ by the LehighCement Company in Allentown, Pennsylvania. Refcon is formed by sinteringa pelletized, solid mixture of bauxite and limestone. A typicalcomposition comprises:

Al₂O₃ & TiO₂ 57.40% Total Iron as Fe₂O₃  1.20% CaO 34.20% SiO₂  5.70%SO₃  0.36%

Refcon typically has a bulk density of about 1500 kg/m3 and a specificgravity of 3.02. It possesses a blaine specific surface of 3300 cm2/g.It has a one day compressive strength of 6500 psi when measured byA.S.T.M. C-109. A preferred magnesium-containing component is Mag-Chem10-40, a compound containing primarily MgO.

The Al₂O₃ fraction of the dry component is preferably at least onepercent and preferably ranges from approximately 1% to approximately 85%by weight. The CaO fraction of the dry component is preferably at leastone-quarter of a percent, by weight.

It should be noted that when monocalcium phosphate is used as a singlesource for both the dry phosphate and dry calcium-providing component,it appears that it is necessary to include the additionalcalcium-providing material mentioned above to achieve adequate bondingto provide dimensional and structural stability to the bonded aggregatestructure when exposed to elevated temperatures of up to 3400 F.

As can be seen from the compositions of these materials, the presentinvention is advantageous in that it permits satisfactory boundaggregate structures to be formed quickly (8 to 30 minutes with adequateworking time (10 minutes or more at 70 F) and be able to withstandtemperatures up to 3400 F using commercial and agricultural gradematerials, including particularly a phosphoric acid such as TG-434,preferably diluted. Bound aggregate structures can be formed by applyingthe binder component and aggregate to a mold, allowing the boundaggregate structure to set, and removing the bound aggregate structurefrom the mold. This method can be used to line or form heat-containingvessels such as kilns, cement kilns, lime kilns, kaolin kilns, furnaces,and incinerators. Examples of furnaces specific for the petrochemicalindustry include fluidized catalytic craking unit or cat cracker (FCCU)cyclones, sulfur reactors, ethylene crackers, and coke calciners. Themethod and bound aggregate can also be used to line or form vessels forcontaining amorphous materials such as molten metals including aluminum,steel, copper, brass, bronze, magnesium, iron and lead. Other productswhich can be constructed by the methods from the bound aggregate of thepresent invention include burner tiles and blocks, thermocouple sleevesand molten material conveying devices such as stock tubes and laundersand troughs.

The invention is also advantageous in that the binder incorporating thepreferred materials described above can be used with a variety ofaggregates for different structural purposes. The binder of the presentinvention can be employed with refractory aggregates, high temperatureinsulation aggregates, and ambient temperature aggregates used inambient applications.

For example, typical aggregates useful for forming a bonded aggregatestructure in accordance with the present invention include at least oneof the following: flint clay, mulcoa, kyanite, mullite, chromite,tabular alumina, silicon oxide, silica, calcined bauxite, chrome oxide,zirconia, phosphate rock, and mixtures thereof. It is believed that someamount of aluminum-containing material is necessary for any denserefractory aggregate structure in order to achieve adequate bonding andmaintain dimensional and structural stability when exposed to elevatedtemperatures.

The preferred refractory aggregates include flint clay; Mulcoa 47, 50,60, 70, and 90;. kyanite; mullites; chrome ore; bauxite; tabularalumina; and mixtures thereof. For alumina based systems, as theintended temperature of use of the refractory increases, the aluminumcontent of the aggregate generally increase as well.

An aggregate useful in the present invention to be used as an expandablehigh temperature insulation may be selected from at least one of: silicasand #140, mullite #200, kyanite #325, tabular alumina #200, dolomiticlime, and talc. A preferred aggregate for expandable insulationcomprises a mixture of silica sand #140, dolomitic lime, and talc. Thetalc controls the size of the bubbles of carbon dioxide released duringexpansion and therefore allows the pores in the expanded insulation tobe uniform in size. A particularly useful aggregate for an ambienttemperature application involving use of this system tocontain/solidify/neutralize liquid waste material (i.e., radioactivewaste material) is phosphate-containing aggregates, preferably phosphaterock (sold as C-31 Phos-Rock by PCS Sales, Inc., Aurora, N.C.).

The chemical composition of these aggregates is well known to thoseskilled in this art. Mulcoa, flint clays, and kyanites are comprised of,in major part, aluminum (III) oxide, silica dioxide (that is, silicontetroxide). Chrome ore is comprised of, in major part, chromium (III)oxide, aluminum oxide, and magnesium oxide. Tabular alumina is comprisedsubstantially of pure aluminum (III) oxide. White sand is comprised of,in major part, silicon dioxide. Lime consists in major part of calciumoxide. White dolomitic lime is a mixture of lime and dolomite (calciummagnesium bicarbonate). Talc is a natural foliated hydrous magnesiumsilicate.

This list of aggregates which can be bound by the binder of the presentinvention is not intended to be an exhaustive list of aggregates usefulin the present invention, but represent testing and conclusions broughtabout by using them. Because of the versatility of the binder system, itis expected that many other aggregates may be bound by the binder systemof the present invention and be used for form useful bound aggregatestructures. Which aggregate to use will be chosen in accordance with theend use requirements of the bound structure and the purity of theproduct needed.

As shown in the following example, a dry aggregate composition inaccordance with the present invention can be formed from a mixture ofabout 50-95 percent by weight of a suitable aggregate, 1-20 percent byweight of a dry calcium- and/or magnesium-providing component, and 0-50percent by weight of a dry phosphate-providing component; and in oneembodiment, from a mixture including 1-30 percent by weight of a singlematerial providing both of the phosphate- and calcium-providingcomponents, as well as an additional calcium component.

Thereafter, depending upon the type of bound aggregate structure that isdesired, from about 5-85 percent by weight of a wet phosphate-providingcomponent is admixed with the dry aggregate composition. For arefractory structure, between 10 and 30 percent by weight of the wetcomponent will typically be employed. However, if it is desired that theadmixed materials be expandable or pumped into the location of use (forexample, if they are used as an expandable insulation or a pumpable hightemperature insulation) more of the wet component will be employed, forexample, preferable between 30 and 60 percent by weight.

Table I recites Examples #1 through #15 which define refractorycompositions falling within the scope of the present invention. Table IIrecites the chemical analyses of the various components. The compressivestrength (psi) and linear re-heat change were measured in accordancewith prevailing A.S.T.M standards. (For example, A.S.T.M. C-133-84—ColdCrushing Strength and Modulus of Rupture of Refractory Bricks and Shapesand A.S.T.M. C-1 13-74—Reheat Change of Refractory Brick). Samples wereprepared for such testing by pouring 2.5 kg increments of the blendedaggregate and binder mixture into an appropriate volume of aqueousphosphate solution and hand-mixing with a two

inch trowel until the mixture is completely wetted out (typically forapproximately one minute) and then depositing the mixture intoappropriately dimensioned molds.

TABLE I EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM-EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- PLE PLE PLE PLE PLE PLE PLEPLE PLE PLE PLE PLE PLE PLE PLE PLE PLE 1 % 2 % 3 % 4 % 5% 6 % 7 % 8 % 9% 10 % 11 % 12 % 13 % 14 % 15 % 16 % 17 % SAMPLE FORMULATIONS Dry ALCOAA-12  18.44%    2%  18.4%  20.34%  20.00%  18.4%  20.34% ALUMINA BAUXITE8X20  59.90%  59.90%  59.90% CAREY MICROFINE  4.00% DOLOMITE CERAMITALC#1  4.00% CHROME SAND  90.00%  93.00% FLINT CLAY  50.15%  50.15% FUSEDSILICA  93.00% KYANITE 100  23.39% MAG CHEM 10-40  2.90%  2.90%  5.00% 2.00% MULCOA 47-4  50.15%  70.20% MULCOA 60-8X0  73.76%  73.76%  73.76%MULCOA 90  60.00%  60.00% MULLITE #200  23.39%  23.39%  20.05% REFCON 6.41%  6.41%  6.41%  6.41%  5.90%  5.90%  14.00%  5.00%  7.00%  5.90% 5.90%  5.00%  7.00%  3.00%  3.00%  3.00% SILICA 140  68.00% TAB ALUM8x0  13.83%  13.00%  15.73%  15.00%  15.73%  95.00% TG C-38  20.05% 20.05%  20.05%  3.34%  1.90%  1.90%  10.00%  2.00%  3.00%  2.00% TOTALDRY 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00%100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00% 100.00%LIQUID TG 434 1:4 13.00% 13.00% 13.00% TG 434 1:3 40.00% TG 434 TG 4341:1 17.00% 14.00% 15.00% 13.00% 14.00% 15.00% 13.00% 13.00% 14.00%15.00% 13.00% 19.00% 19.00% PHYSICAL DATA Cold Crushing ampere ambient3750 6000 6000 4000 3850 4200 6000 2000 1000 538 4500 4200 4000 1500 8162625 2900 2500 2000 3500 3000 2000 1093 4000 4300 3900 1375 7000 50005250 6800 5000 7500 4000 3000 2200 1204 6000 4500 7500 7666 7280 43507200 7800 4550 2400 1316 7000 9000 11500 5487 11000 9500 5750 11800 85003000 2600 1427 9000 12500 6462 14000 10500 6565 13250 9000 2800 15386000 21500 800 10110 13125 22500 5800 9800 12850 21500 5250 3000 16498125 11925 11900 8500 12500 12550 8250 8000 3100 1704 LINEAR REHEATSHRINKAGE 1000 538 −0.10% −0.10% −0.20% 1500 816 −0.50% −0.42% −0.30%−0.10% −0.30% 2000 1093 −1.00% −0.89% −0.50% 0.36% −0.40% −0.42% −0.50%2200 1204 −0.29% −0.372% −0.25% −0.300% −0.33% 2400 1316 −0.90% −0.775%−0.500% 2600 1427  1.34% −1.00%  −0.30% −0.70% 2800 1538 −1.69% −1.50% 3000 1649  1.10% −8.50%  −0.50% SET TIME (Minutes) 8-15 8-15 8-15 8-158-15 8-15 8-15 8-20 8-15 8-15 8-15 8-20 8-20 8-20 8-20 8-20 8-20

TABLE II CHEMICAL ANALYSES OF SAMPLE FORMULATIONS EXAM- EXAM- EXAM-EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- EXAM- PLE 1 PLE 2 PLE 3 PLE 4 PLE 5PLE 6 PLE 7 PLE 8 PLE 9 PLE 10 Al2O3 35.61%  36.25%  37.12%  42.24% 57.51%  78.14%  6.00 79.75%  17.16%  79.77% SiO2 16.87%  16.29%  30.36% 36.35%  24.48%  2.16% 50.99%  2.16% 1.89% 2.13% TiO2 0.31% 0.29% 1.05%1.30% 1.37% 2.23% 0.01% 2.27% 2.23% Fe2O3 0.60% 0.63% 0.96% 0.90% 0.86%0.94% 0.28% 0.94% 0.71% 0.91% CaO 5.67% 5.68% 5.69% 2.52% 2.17% 2.13%5.16% 1.91% 12.77%  1.79% MgO 0.39% 0.39% 0.43% 0.23% 0.18% 0.14% 1.11%0.13% 0.74% 0.11% Na2O 0.13% 0.13% 0.04% 0.05% 0.08% 0.05% 0.01% 0.05%0.05% K2O 0.04% 0.05% 0.03% P2O5 11.95%  11.96%  11.99%  1.97% 1.18%1.11% 4.82% 1.19% 8.46% S 0.00% MnO 0.00% MgCO3 1.29% CaCO3 1.57% R2O3SO3 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.04% 0.02% 0.11% 0.02% F 0.31%0.32% 0.31% 0.09% 0.07% 0.07% 0.17% 0.07% 0.40% 0.04% SO4 0.55% 0.55%0.55% 0.16% 0.11% 0.12% 0.30% 0.11% 0.68% 0.07% H3PO4 1.89% 1.89% 1.89%7.15% 6.04% 6.44% 8.13% 5.68% 28.90%  6.44% Zr2O3 16.04%  16.05% ALKALIES 0.09% 0.17% 0.18% 0.17% Free Water 9.54% 9.55% 9.54% 6.97% 5.896.28% 20.11%  5.54% 28.19%  6.28% EXAM- EXAM- EXAM- EXAM- EXAM- EXAM-EXAM- PLE 11 PLE 12 PLE 13 PLE 14 PLE 15 PLE 16 PLE 17 Al2O3 59.68% 81.50%  19.54%  78.27%  58.17%  83.81%  1.60% SiO2 24.67%  2.13% 1.91%1.99% 24.51%  0.03% 82.26%  TiO2 1.38% 2.27% 2.22% 1.38% Fe2O3 0.83%0.91% 0.55% 0.91% 0.84% 0.19% 0.17% CaO 1.84% 1.54% 11.57%  0.94% 0.98%0.09% 1.32% MgO 0.14% 0.10% 0.55% 2.60% 2.66% 4.49% 1.91% Na2O 0.09%0.06% 0.05% 0.09% 0.10% K2O 0.03% 0.03% P2O5 0.07% 0.07% 1.19% S MnOMgCO3 CaCO3 R2O3 0.01% 0.01% 0.02% 0.01% SO3 0.02% 0.02% 0.12% 0.01%0.01% 0.00% 0.01% F 0.04% 0.04% 0.21% 0.04% 0.04% 0.05% 0.08% SO4 0.06%0.06% 0.34% 0.07% 0.06% 0.09% 0.14% H3PO4 5.66% 5.68% 33.01%  6.44%5.65% 8.26% 8.26% Zr2O3 ALKALIES 0.18% 0.17% Free Water 5.52% 5.54%32.19%  6.28% 5.51% 8.06% 8.06%

It can be seen from the examples in Table I that the binder system ofthe present invention is useful for forming a variety of differentrefractory materials of different utilities from a single binder system.The proportions in the table are adjustable to optimize the resultingaggregate structures, depending upon intended use.

The present invention thus provides a method for forming a bondedaggregate, as well as providing a binder system for such bondedaggregate structures, a dry aggregate composition incorporating the dryconstituents of the binder system, and a mixture of dry constituentsneeded in making the binder system. The present invention isadvantageous over prior binder systems in that the constituents of thebinder system can be commercial and agricultural grade materials, whichhave not been highly refined or purified. The dry binder componentsallow for the use of significantly less expensive aqueous phosphatesolutions, and yet provide a bonded aggregate structure that issignificantly better in refractory applications than is presentlyenjoyed by other known bonded aggregate structures for similarapplications.

Moreover, the present invention advantageously reduces the expense ofproviding a variety of aggregate structures, because a single bindersystem can be employed to bind a wide variety of aggregates. Theinvention reduces the cost of supplying, manufacturing, or keeping ininventory different binder constituents.

With the refractory aggregate composition of the present invention usingsilica and other readily available refractory aggregates, the resultingaggregate structures possess significantly improved refractorycharacteristics over prior art structures in that the resultingstructures are less susceptible to thermal shock, and in many cases, thestructures do not need to be pre-dried or pre-fired after their initialset before being used at high temperatures. In addition, in fieldtesting, the resultant structures proved to be extremely non-wetting toa variety of molten metals (both ferrous and non-ferrous) thus providingthe end user with a low-maintenance refractory lining throughout itsuseful life.

Furthermore, the use of calcium (either alone or in combination withmagnesium) as the divalent binder permits the refractory characteristicsto depend upon the proportion and concentration of the wet and dryphosphate-providing components, specifically a selection of thetemperature range in which optional refractory characteristics areobtained. Such selectivity is absent in mono-aluminum phosphate andmagnesium phosphate-based systems.

In view of the teaching presented herein, other modifications andvariations of the present inventions will be readily apparent to thoseof skill in the art. The foregoing discussion, and description areillustrative of some embodiments of the present invention, but are notmeant to be limitations on the practice thereof. It is the followingclaims, including all equivalents, which define the scope of theinvention.

Any patents or publications mentioned in this specification areindicative of the levels of those skilled in the art to which theinvention pertains. These patents and publications are hereinincorporated by reference to the same extent as if each individualpublication was specifically and individually indicated to beincorporated by reference.

One skilled in the art will readily appreciate that the presentinvention is well adapted to carry out the objects and obtain the endsand advantages mentioned, as well as those inherent therein. The presentexamples along with the methods, procedures, treatments, molecules, andspecific compounds described herein are presently representative ofpreferred embodiments, are exemplary, and are not intended aslimitations on the scope of the invention. Changes therein and otheruses will occur to those skilled in the art which are encompassed withinthe spirit of the invention as defined by the scope of the claims.

What is claimed:
 1. A binder useful for bonding an aggregate into a rigid structure upon mixing and setting of said binder and said aggregate, said binder comprising: an acidic phosphate-providing component, said component being in a liquid phase at ambient temperature and pressure; and a dry component comprising CaO, Al₂O₃, SiO₂, and Fe₂O₃ in proportions adequate to allow working upon mixing of said binder and said aggregate and adequate to yield a rigid structure upon setting of said mixed binder and aggregate, wherein said Fe₂O₃ comprises between 0.8 and 1.0 percent by weight of said binder.
 2. The binder of claim 1, wherein the acidic phosphate component comprises a phosphoric acid.
 3. The binder of claim 1, wherein the acidic phosphate component comprises orthophosphoric acid.
 4. The binder of claim 1, wherein said dry component comprises at least 0.25 percent by weight of said CaO.
 5. A bondable aggregate composition comprising: an aggregate; and a binder, said binder comprising: an acidic phosphate-providing component, said component being in a liquid phase at ambient temperature and pressure; and a dry component comprising CaO,Al₂O₃,SiO₂, and Fe₂O₃ in proportions adequate to allow working upon mixing of said binder and said aggregate and adequate to yield a rigid structure upon setting of said mixed binder and aggregate, wherein said Fe₂O₃ comprises between 0.8 and 1.0 percent by weight of said binder.
 6. The bondable aggregate of claim 5, wherein said acidic phosphate component comprises a phosphoric acid.
 7. The bondable aggregate of claim 5, wherein said acidic phosphate component comprises orthophosphoric acid.
 8. The bondable aggregate composition of claim 5 further comprising a porosity-providing component, said component comprising low melting point particles dispersed evenly throughout said composition.
 9. A method for forming a bonded aggregate structure, said method comprising the steps of: admixing a wet or aqueous phosphate-providing component with a dry aggregate composition to form a mixture, said dry aggregate composition containing an aggregate and a binder component, said binder component comprising CaO,Al₂O₃,SiO₂, and Fe₂O₃ in proportions adequate to yield a settable mixture, wherein said Fe₂O₃ comprises between 0.8 and 1.0 percent by weight of said mixture; and allowing said mixture to set.
 10. The method of claim 9, wherein phosphate-providing component comprises a phosphoric acid.
 11. The method of claim 9, wherein phosphate-providing component comprises orthophosphoric acid.
 12. The method of claim 9 further comprising applying said mixture into a mold during or after said admixing step in order to form a bonded aggregate structure.
 13. The method of claim 12 further comprising removing said bonded aggregate structure from said mold after said setting step.
 14. The method of claim 12, wherein said mold comprises a compound selected from the group consisting of steel, wood, foam, or plastic.
 15. The method of claim 9 and further comprising applying said mixture onto a heat-containing vessel during or after said admixing step in order to line said vessel.
 16. The method of claim 15, wherein the heat-containing vessel is an incinerator.
 17. The method of claim, 15, wherein the heat-containing vessel is a kiln.
 18. The method of claim 15, wherein the heat-containing vessel is a cement kiln.
 19. The method of claim 15, wherein the heat-containing vessel is a line kiln.
 20. The method of claim 15, wherein the heat-containing vessel is a kaolin kiln.
 21. The method of claim 13, wherein the heat-containing vessel is a furnace.
 22. The method of claim 21, wherein the furnace is a fluidized catalytic cracking unit.
 23. The method of claim 21, wherein the furnace is a sulfur reactor.
 24. The method of claim 21, wherein the furnace is an ethylene cracker.
 25. The method of claim 21, wherein the furnace is a coke calciner.
 26. The method of claim 9 further comprising applying said mixture into a vessel for containing an amorphous material during or after said admixing step in order to contain said amorphous material.
 27. The method of claim 26, wherein said amorphous material comprises a molten metal.
 28. The method of claim 27, wherein the metal comprises aluminum.
 29. The method of claim 27, wherein the metal comprises steel.
 30. The method of claim 27, wherein the metal comprises copper.
 31. The method of claim 27, wherein the metal comprises iron.
 32. The method of claim 22, wherein the metal comprises brass.
 33. The method of claim 22, wherein the metal comprises bronze.
 34. The method of claim 27, wherein the metal comprises magnesium.
 35. The method of claim 27, wherein the metal comprises lead.
 36. The method of claim 12, wherein the bounded aggregate structure is a burner tile or block.
 37. The method of claim 12, wherein the bounded aggregate structure is a thermocouple sleeve.
 38. The method of claim 12, wherein the bonded aggregate structure can convey a molten material therein.
 39. A binder useful for bonding an aggregate into a rigid structure upon mixing and setting of said binder said aggregate, said binder comprising: an acidic phosphate-providing component, said component being in a liquid phase at ambient temperature and pressure; and a dry component comprising CaO,Al₂O₃,SiO₂, and Fe_(2O) ₃ in proportions adequate to allow working upon mixing of said binder and said aggregate and adequate to yield a rigid structure upon setting of said mixed binder and aggregate, wherein said Fe₂O₃ comprises approximately 1.0 percent by weight.
 40. A binder useful for bonding aggregate into a rigid structure upon mixing and setting of said binder and said aggregate, said binder comprising: an acidic phosphate-providing component, said component being in a liquid phase at ambient temperature and pressure and comprising SO₄; and a dry component comprising CaO,Al₂O₃,SiO₂, and Fe₂O₃ in proportions adequate to allow working upon mixing of said binder and said aggregate and adequate to yield a rigid structure upon setting of said mixed binder and aggregate.
 41. A binder useful for bonding an aggregate into a rigid structure upon mixing and setting of said binder and said aggregate, said binder comprising: an acidic phosphate-providing component, said component being in a liquid phase at ambient temperature and pressure, said phosphate-providing component having a specific gravity between approximately 1.14-1.71; and a dry component comprising CaO,Al₂O₃,SiO₂, and Fe₂O₃ in proportions adequate to allow working upon mixing of said binder and said aggregate and adequate to yield a rigid structure upon setting of said mixed binder and aggregate. 